CSU Fisheries Ecology
Forensic Applications of Otolith Microchemistry for Tracing Sources of Illegally Stocked Fishes
Funded by: Whirling Disease Initiative, Montana Water Center
Students and Postdocs
Patrick Martinez, Colorado Division of Wildlife
Dana Winkelman, Colorado Cooperative Fish and Wildlife Research Unit, Colorado State University
Alan Koenig, USGS Mineral Resources Laboratory, Lakewood, CO
Gregory Whitledge, Department of Zoology, Southern Illinois University
One of the continued threats to viable trout populations in the Mountain West is the spread of whirling disease via illegal stocking of diseased trout. Attempts to halt such introductions and prosecute violators have been thwarted because it has been virtually impossible to trace the origins of a diseased trout once it has been stocked. Naturally occurring chemical markers in fish tissue have shown promise as a method to track the origins of fish in previous studies. However, research to date had not looked at the potential for these markers to work adequately in hatchery environments over large areas or to distinguish many potential source hatcheries. We evaluated the use of chemical markers in fish otoliths, or “ear stones,” to determine the hatchery of origin of stocked trout.
We found that otolith markers could be highly effective markers of the past environmental history of trout. We sampled 11 hatcheries and several populations of stocked trout captured from public waters, simulating conditions that may occur in a forensic case. Our ability to correctly identify the hatchery the fish came from increased with the number of chemical markers used (and hence cost) and when there were fewer “suspect” hatcheries. Otoliths are capable of providing information about the location a fish has inhabited, a feat not achievable with any other technique. The information from otoliths is best used to fill gaps in cases where traditional methods of investigation have been adequately conducted. The result of this research will provide law enforcement with a valuable tool to prosecute those who have illegally stocked trout and serve as a deterrent to future illegal stockings. Thus, we have provided a useful tool to help preserve the biological and economic health of trout fisheries.
FINAL REPORT (pdf)
Dr. Brett M. Johnson
Department of Fish, Wildlife and Conservation Biology
1474 Campus Delivery, Colorado State University,